JMeter Run time assertion vs regex - jmeter

Question

I have an request which uses a variable previously set. Asserting this variable to check the value doesn't exist within the response. Then resetting the variable to blank to check other apis
Example
UDV - var1 = "ABC"
Request1
- Assert var1 doesn't exist
- Regex extractor set var1 (use empty default value)
Request2
- Check var1 (which will be blank)
I can't do the same check as before as i reuse the modules. So just want to set it to blank.
Expected: First check is executed with var1 set to "ABC" and then sets var1 to blank for next request
Actual sets var1 to blank then does the check in request1 so fails the request.
Any ideas?

Answer 1

As per Execution Order of JMeter Test Elements:
0 Configuration elements
1 Pre-Processors
2 Timers
3 Sampler
4 Post-Processors (unless SampleResult is null)
5 Assertions (unless SampleResult is null)
6 Listeners (unless SampleResult is null)
As you can see, Regular Expression Extractor is a Post-Processor so it is executed before the assertion.
If you need to make var1 value blank:
Remove Regular Expression Extractor
Add JSR223 Listener as a child of the Request 1 and put the following code into "Script" area:
vars.remove('var1') // if you want to delete the variable
vars.put('var1', '') // if you want the variable to be a blank string
Where vars stands for JMeterVariables class instance, check out JavaDoc for more information on its functions and Top 8 JMeter Java Classes You Should Be Using with Groovy article to learn more about other JMeter API shorthands